DESCRIPTION: (Adapted from the applicant's abstract.) It is hypothesized that the cellular and temporal pattern of expression of the GRP receptor is critical in determining the action of the peptide. This will be studied through a program focused on the characterization of the gastrin releasing peptide receptor. Furthermore, antibodies directed against the GRP receptor will be produced and used as highly specific antagonists. Specific Aims include the following: 1. Development of immunologic and molecular reagents with which to study GRP receptor. 2. Analysis of GRP receptor cDNA sequence and deduction of GRP receptor structure and function. 3. Descriptive studies of GRP receptor expression. 4. Interference of GRP action in lung development using receptor-directed agents.